Rotary actuator with selectable response characteristics

Abstract

A rotary actuator is disclosed useful in controlling throttle settings on internal combustion engines. The angular displacement of the actuator shaft is a function of the current applied to the actuator. In the disclosed embodiment the relationship between current and angular displacement has three distinct regions: increasing displacement, linear displacement and decreasing displacement with respect to applied current. These regions are matched to the engine characteristics to produce a desired response from the engine. The actuator consists of a rotor biased by a coil spring to a first position and displaceable to a plurality of intermediate positions by magnetic actuation from pole pieces associated with current carrying coils. The arrangement and configuration of the rotor and pole pieces produce the desired three region response characteristic.

I claim: 
     
       1. A variable position rotary actuator having a selectable response characteristic comprising: (a) a housing formed of nonmagnetic material,   (b) an output shaft mounted for rotation between first and second positions in said housing and extending therefrom for connection to a device to be controlled by said actuator.   (c) means for biasing said rotor to said first position, out of alignment with said pole pieces,   (d) magnetic circuit means in said housing including: electrical coils, pole pieces associated with said coils, a rotor secured to said shaft for movement therewith, said rotor and shaft being angularly displaceable to a selectable position intermediate said first and second positions by magnetic force when electric current is passed through said coils, said intermediate position being a function of the magnitude of the current passing through said coils,   (e) said rotor and pole pieces having a geometric configuration producing a current versus angular displacement characteristic having three distinct regions including a linear region and regions of increasing and decreasing angular displacement.   
     
     
       2. A variable position rotary actuator having a selectable response characteristic comprising: (a) a housing,   (b) an output shaft mounted for rotation between first and second positions in said housing and extending therefrom for connection to a device to be controlled by said actuator,   (c) means for biasing said shaft to said first position,   (d) electrically energized magnetic circuit means for angularly displacing said shaft from said first position to any of a number of positions intermediate said first and second positions as a function of the magnitude of the electric current applied to said magnetic current means,   (e) said magnetic circuit means including a rotor attached to said shaft for movement therewith and pole pieces to which the rotor is magnetically attracted, the geometric configuration of said rotor and pole pieces producing a current versus angular displacement of the shaft characteristic having three distinct regions including a linear region and regions of increasing and decreasing angular displacement.   
     
     
       3. A rotary actuator according to claim 1 or claim 2 further including means for limiting the movement of said shaft to select said first position and the maximum angular displacement therefrom. 
     
     
       4. A rotary actuator according to claim 3 wherein said limiting means is a stationary stop member and a pin secured to said rotor for movement therewith, said pin engaging said stop member to restrict movement of said shaft. 
     
     
       5. A rotary actuator according to claim 1 wherein said magnetic circuit has two electrical coils and two pole pieces, said pole pieces being disposed on opposite sides of said output shaft. 
     
     
       6. A rotary actuator according to claim 1 or claim 2 wherein said biasing means is a coil spring. 
     
     
       7. A rotary actuator according to claim 1 claim 2 wherein said rotor is an elongated member, the ends of which are magnetically attracted to said pole pieces to produce angular displacement of said shaft, each of said rotor ends being curved in a convex manner, the radius of the curvature of each end being taken from a point spaced from the center of said rotor, each of said points being equidistant from the rotor center and on opposite sides thereof. 
     
     
       8. A rotary actuator according to claim 7 wherein the surface of each pole piece to which an end of said rotor is magnetically attracted is curved in a concave manner, complimentary to the curvature of the rotor end, whereby a variable gap or spacing between the rotor ends and each pole piece is defined, the variable gap producing the desired three region current versus angular displacement response characteristic.   
     
     
       9. A rotary actuator according to claim 7 wherein the distance of each point from said center is greater than 0.04 inches. 
     
     
       10. A rotary actuator according to claim 7 wherein said points define a line perpendicular to the longitudinal direction of said rotor.